One of the basic problems in bone remodelling is the quantification and mechanism of mineral and collagen conservation. The interaction of mineral with collagen and how this interaction relates to their conservation and destruction are not understood at this time. The objective of these studies is to investigate the mechanisms of how the body handles mineral and mineralized collagen at a physiologcal and biochemical level during various treatments and ages. We have developed procedures that will aid in elucidating the turnover of mineral and collagen under normal and pathological conditions in young and adult animals. The experimental design is to quantify the turnover of old and accumulation of new minerals and mineralized collagen in chronically labeled animals over intervals of time after labeling when the animal has reached a steady state, isotopically and biologically. Since the phenomena of calcium loss and calcium conservation, and collagen loss and collagen reutilization are both known to exist, these studies should help to estimate the relative proportion between destructive and non-destructive bone turnover. Quantitative kinetics will be done in normal and mutant animals for: (1) vitamin D deficient and toxic states; (2) parathyroid deficient and toxic states; (3) disuse remodelling; (4) calcium deficient state during lactation; (5) effect of aging on bone remodelling. Effects of (1)-(4) on ionic and complexed serum calcium will be studied. The concept of non-isotopic turnover and conservation of macromolecules would provide a new biological basis for studying normal and pathological remodelling, and aging; and for elucidating the biological controls of a balance between destructive and conservative turnover of mineralized collagen and mineral, particularly in light of the tight coupling between bone resorption and bone formation.